import sequtils,strutils
var
    D = stdin.readline.parseInt
    A = stdin.readline.split.map(parseInt)
for i in countdown(D,3):
    A[i - 2] += A[i]
    A[i] = 0
var
    D2 : int
    b = newSeq[int](0)
for i in 0..2:
    if A[i] != 0:
        D2 = i
for i in 0..D2:
    b.add(A[i])
echo D2
echo b.join(" ")